Emesis is the act of vomiting and can be described as the forceful expulsion of gastrointestinal contents through the mouth brought about by the descent of the diaphragm and powerful contractions of the abdominal muscles. Emesis is usually, but not always, preceded by nausea. Retching (or dry heaves) involves the same physiological mechanisms as vomiting, but occurs against a closed glottis. Nausea may be defined as a desire to vomit but which is not associated with expulsive muscular movement.
Vomiting, nausea, retching or any combination (hereinafter referred to as “the symptoms”) can be caused by a number of factors including anaesthetics, radiation, cancer chemotherapeutic agents, toxic agents, medicines, for example serotonin reuptake inhibitors, analgesics such as morphine, antibiotics, pregnancy and motion. Conditions which are associated with vertigo, for example Meniere's disease, can also cause the symptoms. Headache, caused by for example migraine, increased intracranial pressure or cerebral vascular haemorrhage can also result in the symptoms. Other maladies associated with the symptoms include cholecystitis, choledocholithiasis, intestinal obstruction, acute gastroenteritis, perforated viscus, dyspepsia resulting from, for example, gastroesophogeal reflux disease, peptic ulcer disease, gastroparesis, gastric or oesophageal neoplasms, infiltrive gastric disorders (e.g. Menetrier's syndrome, Crohn's disease, eosinophilic gastroenteritis, sarcoidosis and amyloidosis), gastric infections, parasites, chronic gastric volvulus, chronic intestinal ischaemia, altered gastric motility disorders and/or food intolerance or Zollinger-Ellson syndrome. In some cases of the symptoms, no etiology can be determined, as for example in Cyclic Vomiting Syndrome.
The symptoms may be defined as acute when they are present for less than a week. The causes of the symptoms of short duration can be separable from etiologies leading to more chronic symptoms. The symptoms may be defined as chronic when they are present for over a week; these can be continuous or intermittent, and last for months or years.
Two areas of particular clinical relevance are nausea and vomiting resulting from surgical procedures (post-operative nausea and vomiting, or PONV) or chemotherapeutic agents and radiation therapy (chemotherapy-induced nausea and vomiting, or CINV). The symptoms caused by chemotherapeutic agents can be so severe that the patient refuses further treatment. Three types of emesis are associated with the use of chemotherapeutic agents, i.e. acute emesis, delayed emesis and anticipatory emesis.
PONV is a significant issue for patients and healthcare providers. It is rated second only to pain as the complication most feared by patients, and contributes significantly to anxiety and patient distress. Vomiting can have an adverse impact on surgical wound sites, especially upper GI tract surgery.
Risk factors for PONV include type of surgery, gender (women are more prone than men to PONV), smoking history, prior history of PONV or motion sickness, length of surgery, use of volatile anaesthetics and opioid analgesic usage. Certain operations seem to be particularly associated with PONV, including procedures on the eyes and ears, laparoscopic cholecystectomy and hysterectomy, breast surgery and major abdominal and gynaecological surgery.
PONV is typically treated using a dopamine D2 antagonist such as droperidol. This drug was given a black box warning by the FDA in 2001 on the basis of cardiotoxicity, believed to be related to a propensity of the drug to block HERG channels and cause QT prolongation.
Amisulpride, an atypical antipsychotic D2 antagonist, has beneficial actions in schizophrenic patients. For patients characterised by predominant negative symptoms, oral doses of 50-300 mg/day are recommended. It is reported in the UKPAR (Special Warnings and Precautions for Use) that amisulpride induces a dose dependent prolongation of the QT interval.
Amisulpride is marketed as Solian, a solution for intramuscular administration, comprising water, hydrochloric acid, sodium chloride and amisulpride. An ampoule contains amisulpride at 200 mg/4 ml solution.
U.S. Pat. No. 4,294,828 discloses amisulpride and related compounds having anti-apomorphine and anti-serotonin activity. Amisulpride is reported to inhibit apomorphine-induced vomiting in the dog, thereby confirming that amisulpride is a functional D2 antagonist. It is suggested that the compounds should be administered at doses of 50-750 mg/day, e.g. 200 mg/day.